COLLODION AND OTHER IMBEDDING METHODS. 131 



of the thyme oil. But later (June, 1895), writing to me, 

 Dr. Fish says he has substituted the white oil of thyme for 

 the red, and finds it an advantage in orientating. See also 



Some specimens of clove oil dissolve collodion very slowly, and may be 

 used, but I would not be understood to recommend it. The action of 

 origanum oil varies much, according to the samples ; some sorts do not 

 clear the collodion, others dissolve it, others pucker it. MIXOT (Zeit. f. wiss. 

 3/Vfc., iii, 2, 1886, p. 175) says that Dunham's mixture "clarifies the sec- 

 tions very readily, and softens the celloidin just enough to prevent the 

 puckering, which is so annoying with thyme alone." 



Carbolic acid has been recommended. WEIGEET (Zeit. f. wiss. Mik., iii, 

 4, 1866, p. 480) finds that a mixture of 3 parts of xylol with 1 part of 

 carbolic acid (anhydrous) clears well. But it must not be used with the 

 basic anilin stains, as it discolours them. For these anilin oil may be used 

 with the xylol in the place of carbolic acid. 



Anilin oil clears well (it will clear from 70 per cent, alcohol), but unless 

 thoroughly removed the preparation becomes yellowish-brown. This colora- 

 tion may be removed by soaking in chloroform for twenty-four hours (see 

 VAN GIESON, Amer. Mon. Mic. Joum., 1887, p. 49, or Journ. Roy. Mic. 

 Soc., 1887, p. 519, for a review of these clearing agents ; see also 121). 



Beech-wood creasote has been recommended (by M. Flesch). 



EYCLESHYMER (Amer. Nat., xxvi, 1892, p. 354 ; Journ. Roy. Mic. Soc., 

 1892, p. 565) advises a mixture of equal parts of bergamot oil, cedar oil, and 

 carbolic acid. 



For oil of cajeput see 116; and for this and other 

 clearers see also the paper of JOBDAN quoted 107. 



162. Review of the Older Celloidin Method. The older cel- 

 loidin method, described in the foregoing pages, is extremely 

 lengthy and cumbrous. The operation of infiltrating the 

 tissues with the collodion requires days or weeks. The 

 hardening process frequently requires nearly as much time. 

 The resulting mass has the disadvantage of being opaque, or 

 at most only translucent, not transparent. The mass has to 

 be cut under the surface of alcohol, or at least with constant 

 wetting with alcohol, and with a knife kept constantly wet 

 with alcohol. By the recent method of clearing the mass 

 before cutting a large part of these defects is done away 

 with ; the resultant mass is as clear as glass, thus allowing the 

 most perfect orientation of the object ; and, as I have shown 

 (LEE et HKNNEGOY, Traite des Mtthodes techniques de I'Anat. 

 mic., 1896, p. 230), the mass can with advantage be cut dry, 



